In the past, automobiles and other vehicles have been equipped with antennas enabling the reception of radio waves even during movement. Generally, the radio waves received by a vehicle have for long years principally been the medium waves (MW) for AM radio and the very high frequency (VHF) or ultrahigh frequency (UHF) waves for FM radio or television.
However, in recent years, the types of antennas mounted at vehicles have been increasing. For example, antennas for global positioning systems (GPS) or antennas for receiving radio waves for digital terrestrial broadcasts have been increasingly becoming mainstream. Antennas receiving radio waves for digital terrestrial TV broadcasts hereinafter will be referred to as “DTV antennas”.
Circularly polarized waves have been used for the GPS radio waves or terrestrial digital TV broadcast radio waves received by such antennas mounted on vehicles. Further, for conventional circularly polarized wave antennas, patch antennas have usually been used. However, such a patch antenna is contained inside an antenna case. The case is tall and therefore the appearance was bad. Therefore, recently, film antennas used attached to the windows of the vehicles have been used (for example, see Japanese Patent Publication (A) No. 2005-102183).
However, the film antennas disclosed in Japanese Patent Publication (A) No. 2005-102183 etc. were not sufficient in reception performance.